Norleucine: A branched-chain amino acid analog affecting feeding behavior of rats

Jean K. Tews, Joyce J. Repa, Alfred E. Harper

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Norleucine, an isomer of leucine and isoleucine and a potent competitor of large neutral amino acid transport into brain, thereby depleting certain amino acid pools, was tested for its effects on growth and feeding behavior of rats fed an amino acid diet limiting in leucine. Growth and food intake were depressed in proportion to the dietary level of norleucine (0.2 to 1.1% of the diet). With suboptimal amounts of indispensable amino acids, leucine at 150% of the requirement reversed the effects of 0.2 and 0.5% norleucine; slight excesses of the other indispensable amino acids were required with extra leucine for maximum growth with 1.1% norleucine. Rats almost exclusively preferred the control to the norleucine diet, but not if the latter diet also contained leucine. Rats also strongly selected a nonprotein rather than norleucine diet when this was the first available choice. If the first choice was between the nonprotein and control diets, rats later almost exclusively selected the norleucine-containing rather than the nonprotein diet for varying periods (2 to 6 days). These studies suggest that amino acid analogs may be useful agents in the study of animal behavior associated with changes in brain amino acid pools.

Original languageEnglish (US)
Pages (from-to)911-921
Number of pages11
JournalPharmacology, Biochemistry and Behavior
Issue number4
StatePublished - Apr 1990


  • Amino acid analog
  • Behavior
  • Diet
  • Food choice
  • Food intake
  • Growth
  • Large neutral amino acids
  • Leucine
  • Norleucine

ASJC Scopus subject areas

  • Biochemistry
  • Toxicology
  • Pharmacology
  • Clinical Biochemistry
  • Biological Psychiatry
  • Behavioral Neuroscience


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